JP2003032482A - Image processing apparatus, its control method, computer program and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce JPEG compression image data in a simple configuration at a desired reduction ratio while suppressing a consumed memory capacity. SOLUTION: A Huffman decoder (102) decodes JPEG compression image data and an inverse quantization circuit 103 applies inverse quantization to the decoded data. When a reduction rate of S/8 (S=1, 2, etc.), is designated, a reduction circuit 104 uses a DC component DC of frequency components for the origin, validates the data of S×S and outputs data of zero for the other. An inverse DCT circuit 105 receives the output of the circuit 104 to apply inverse DCT to the output. A pixel reduction circuit packs S×S pixels in the image after inverse DCT and outputs the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for reproducing and outputting JPEG compressed image data, a control method therefor, a computer program and a storage medium.

[0002]

2. Description of the Related Art In conventional image editing in an imaging device such as a color copier, a manuscript sheet is placed on a digitizer (coordinate input device) or the like, a trimming position or the like is designated, and based on the position information I was scanning and printing.

In recent years, along with the cost reduction of memories and the improvement of compression technology, multi-function color imaging equipment having an electronic sort function has been introduced. Image editing in an imaging device that requires spooling such a page image in a memory is not performed by a digitizer or the like, but rather a display device such as a color liquid crystal is used and a preview display is performed on the operation screen.
Interactive editing is preferred.

[0004]

By the way, the original purpose of such an imaging device is print output. The printing resolution of recent printer engines has become higher. Most of them are 600 dpi or higher. Therefore, if the read image is simply spooled as it is, the memory becomes less expensive, but it requires a huge capacity and inevitably needs to be compressed.

On the other hand, a display device such as a liquid crystal display device for performing a preview generally has a display resolution of 72 dp.
It is about i. Therefore, in order to perform the preview, it is necessary to decompress the compressed high-resolution image into a plain image and perform resolution conversion to generate a reduced image for preview. At this time, the compressed image is expanded. Therefore, the larger the difference in resolution, the larger the work memory is required. Further, since the preview is on the operation screen, it is necessary to frequently change the scaling of the image even after the preview image is displayed. However, if a reduced image is generated from a high-resolution image every time, it takes a long time to generate a preview image, which causes a problem that the response speed of the display becomes slow and the operability of the device deteriorates. is expected. In order to improve the reaction speed, generating preview images of a plurality of resolutions is one means, but this consumes a large amount of memory capacity.

The present invention has been made in view of the above problems, and makes it possible to reproduce JPEG-compressed image data at a desired reduction ratio with a simple structure and suppressing memory consumption. An image processing apparatus, a control method thereof, a computer program, and a storage medium are provided.

[0007]

In order to solve such a problem, for example, an image processing apparatus of the present invention has the following structure. That is, an image processing device for reproducing JPEG-compressed image data, in which a reducing unit that reduces the given JPEG-compressed data in MCU units, and an MC in the reducing unit.
Reducing means for reducing invalidated data when reducing by U, and storing means for packing and storing each image block generated based on the result reduced by the reducing means,
Output means for outputting the image stored in the storage means.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

A block diagram of the JPEG decompressor in the embodiment is shown in FIG. 1 and will be described below.

The JPEG bit stream to be decompressed is
First, it is input to the Huffman decoder 102 and decompresses the Huffman-coded bit stream into quantized spatial frequency data. Subsequently, the quantized spatial frequency data is input to the inverse quantization circuit 103, and the quantized spatial frequency data is expanded to the original number of bits (here, 8 bits) and aligned to 8 bits. Spatial frequency data is generated. Spatial frequency data arranged in 8 bits is reduced by the reduction circuit 1 in MCU unit (8 × 8 pixels).
It is input to 04.

The reduction circuit 104 operates according to an external control signal (magnification designating signal). In the case of the same size, nothing is done, and in the case of generating a reduced image, it is reduced in the frequency space by a magnification of 1/8 to 7/8. In the case of 1/8 reduction, reduction processing is not performed, and only the DC (direct current) component obtained by the above processing is the origin of the MCU (upper left corner of the 8 × 8 matrix).
, And the other spatial frequency components are 0. Further, in the case of 4/8 times, 4 × 4 data having the origin of the MCU (the position with the DC component) as the upper left corner and data of 0 for other spatial frequency components are output. That is, in the case of S / 8 times (S = 1, 2, ..., 8), S × S data whose origin is the DC line segment DC of 8 × 8 data after dequantization is output, and Data other than 0 is output as 0.

The reduced or unchanged spatial frequency data is returned by the inverse DCT circuit 105 to image data in MCU units. The data returned to the image of MCU unit is
It is input to the pixel reduction circuit 106 and is a normal JPEG of the same size.
In the case of decompression, the 8 × 8 pixel image is output as is,
In case of contraction / expansion (depending on control signal), for example, 7/8
If double, 7 × 7 pixels are clipped and output from the origin of the MCU. By performing this process for all JPEG bit streams, JPEG decompression can be performed, and at the time of reduction, the scale factor is reduced to 1/1,
Images of 7/8, 6/8, 5/8, 4/8, 3/8, 2/8, 1/8 will be obtained.

FIG. 2 is a schematic diagram showing the one-dimensional operation of the reduction circuit 104. The images arranged in the frequency space are reduced (6/8 times in this case) and output as the data in the lower part of the figure. The actual reduction circuit 104 performs this processing for the two dimensions of X and Y.

FIG. 3 is a schematic diagram showing how an image is reduced. 8x8 pixel MCU3 compressed in JPEG format
01 is reduced to 6/8 times by the reduction circuit 104, and an image 311 of 6 × 6 pixels is obtained by the pixel reduction circuit 106.
Is expanded in memory as. The following MCU 302 is also 6 /
It is reduced by a factor of 8 and developed as an image 312 on the memory without a space from the image 311. By repeating this, a reduced image is generated.

FIG. 4 is a block diagram showing the system configuration of the imaging device (digital color copying machine) of this embodiment. The JPEG decompressor shown in FIG. 1 is adopted in the JPEG decoder 101 in FIG. The CPU 402 also outputs the control signal in FIG. Hereinafter, the configuration of FIG. 4 will be described together with its operation.

The image scanned by the scanner 406 is taken into the inside of the multifunction controller 401 via the scanner interface 407. The captured image is stored in the main memory 403 via the crossbar circuit 404. The CPU 402 compresses the captured image and spools it in the main memory 403. The spooled image is a JPEG decompressor 10
1 is used to decompress once into a 1/8 resolution plane image, and then is again JPEG compressed as a 1/8 resolution image for preview and stored in the memory 403. As a result, the main memory 403 stores the read image resolution JPEG data and 1/8 JPEG data.

The CPU 402 determines the size of the preview image, and extracts a plain image of a desired resolution from the high resolution original image or the preview 1/8 image to the JPEG decompressor 10.
1 and copy (transfer) to the VRAM 413 of the display unit 411. The plain image copied to the VRAM 413 is displayed on the LCD 412 as a preview image.
Is displayed in. The display unit 411 is provided with an input unit 414 for inputting various instructions, one of which is a coordinate input plate (touch panel) provided on the front surface of the LCD 412.

The spool compressed image data designated for printing by the user is decompressed by the image decompression circuit 101, rotated by the image processing circuit 410, and then printed on paper by the printer 408 via the printer interface 409. Further, in the case of the network scan operation, the spooled compressed image data is sent to the host 413 via the network interface 405.

FIG. 5 is a schematic diagram showing the page image format of this embodiment. One page image is divided into 32 × 32 pixel tiles, and JPEG compression is performed in tile units. An A4 600 dpi image corresponds to 155 x 216 tiles. A reduced image of 1/8 resolution corresponds to 20 × 27 tiles. 32 × 32 pixels is 8 × 8 when compressed by JPEG
It is further divided into MCUs of pixels. JPEG decompressor 10
1 reduces the image in units of this MCU.

FIG. 6 is a flowchart showing the sequence of the preview operation (mainly the CPU 402).
It should be noted that in the following description, the document image from the scanner 406 is J
It is assumed that it is PEG-compressed and read into the main memory 403.

First, a high-resolution original image (main memory 4
(Stored in 03) using the JPEG decompressor 101 to create a 1/8 resolution plane image (step S601). Subsequently, the created 1/8 resolution plane image is divided into tiles shown in FIG. 5, and JPEG compression is performed in tile units (step S602). As a result, the JPEG compressed data of each of the original high resolution image and the 1/8 resolution image is held in the memory 403 (step S603).

Then, from the image of 1/8 resolution, JPEG
The decompressor 101 is set to the 4/8 times reduction mode to create a 1/16 resolution plane image used for the actual preview (step S604). And 1/16
By copying the plane image of the resolution to the VRAM 413, the preview image can be displayed on the LCD 412 (step S605).

Then, the display unit 411 indicates whether the user wants to enlarge or reduce the preview image.
It is determined from the input unit 414 of (step S
606) If the user operation is enlargement or reduction, then it is determined whether the resolution is higher than 1/8 resolution (step S
608), if the resolution is high, the tiles required for display are cut out from the original high resolution image using the tile management information (step S609), and the desired tile of the cut out high resolution image is extracted using the JPEG decompressor 101. A plane image is created at a desired reduction ratio (step S610),
An enlarged display is performed by copying the plane image to the VRAM 413 (step S605).

If the display request image has a lower resolution than the 1/8 resolution, a desired tile is cut out from the 1/8 resolution JPEG compressed image data (step S6).
11), a plane image is created from the desired tile of the cut-out 1/8 resolution image using the JPEG decompressor 101 at a desired reduction ratio (step S612), and the preview image is displayed by copying the plane image into the VRAM 413. Perform (step S605). As a result, 1 /
1 by using JPEG compressed image data of 8 resolution
A reduction ratio of / 8 to 1/64 can be obtained.

If the user's operation is neither the enlargement nor the reduction of the preview, then it is judged whether the preview processing of the image is finished (step S607). If not, it is judged whether the operation is an enlargement operation or a reduction operation. Return (step S6
06), if it is finished, it is judged whether or not it is the preview processing of another image next (step S608). If it is the preview of another image, the JPEG decompressor 101 creates a 1/8 resolution plain image of the other image. (Step S601),
If it is not the preview processing of another image, the preview processing ends.

FIG. 7 is a schematic diagram showing how a preview image is displayed in this embodiment. At the beginning of the preview process, an image 701 having a 1/16 resolution of the entire page is displayed on the LCD 412. When the user specifies enlargement (touches the enlargement button), the CPU 402 determines an enlargement request (step S606), and since the user's request is to double the preview image, the image has 1/8 resolution. In the resolution judgment (S608), the 1/8 resolution retained image is selected, and the tiles necessary for the display that touch the origin of the 1/8 resolution image are cut out (step S611).
A 1/8 resolution image preview plane image is created by unfolding the image by the EG decoder 101 (step S612), and the image is VRA.
The enlarged preview image 702 is displayed on the LCD 412 by copying it to M413.

In the above example, the enlargement and reduction of the preview display when the document is read have been described, but the editing process such as trimming is performed as a separate process. In any case, when the editing process is completed, the process according to the editing instruction is performed, and the printer engine 408
Will be printed out.

As described above, according to this embodiment, it is possible to perform image reduction up to ⅛ times at the same time as JPEG decompression, work memory can be reduced, and high resolution can be achieved by using a JPEG decompressor. By dividing the image into tiles, JPEG compressing each tile and holding and managing it, generating and holding a low resolution image from this high resolution image, cutting out in tile units, JPEG decompression, scaling It is possible to perform the preview process of the display unit of the imaging device at high speed.

Further, according to the present embodiment, the original document is stored in JPEG compression and the plane image of the 1/8 resolution is further stored in JPEG compression.
It is possible to freely generate an image having a resolution of 8/8 to 1/8 and 1/8 to 1/64.

Further, in the embodiment, an example in which the invention is applied to a copying machine has been described. However, the invention may be applied to any device as long as an image is preview-displayed. Not something.

Further, the compression and decompression processing in the above embodiment can be applied to a general-purpose information processing device such as a personal computer for reading the data from a scanner or a storage medium storing JPEG compressed data and displaying the data. . In this case, most of the processing (the portion corresponding to the block diagram of FIG. 1 and the processing according to the flowchart of FIG. 6) is performed by software, so the present invention can also be applied to software installed in an information processing apparatus. When installing software on a computer,
Usually, a storage medium (a floppy (registered trademark) disk, a CDROM, or the like) storing the program is set in the device and copied or installed. Therefore, naturally, such a storage medium is also included in the present invention. Be done.

[0032]

As described above, according to the present invention, J
It is possible to reproduce the PEG-compressed image data with a desired reduction rate with a simple structure and suppressing the memory consumption.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a JPEG decompressor according to an embodiment.

FIG. 2 is a schematic diagram showing the operation of the reduction circuit according to the embodiment.

FIG. 3 is a schematic diagram showing a state before and after image reduction in the embodiment.

FIG. 4 is a system block configuration diagram in the embodiment.

FIG. 5 is a diagram showing an image format in the embodiment.

FIG. 6 is a flowchart showing an operation process of a preview operation of the embodiment.

FIG. 7 is a schematic diagram showing a display state in the embodiment.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 7/30 H04N 5/91 JF term (reference) 5B057 AA20 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CD05 CG05 5C053 FA04 FA05 FA07 GA11 GB36 5C059 KK38 LC04 MA23 PP01 PP14 SS20 SS28 UA02 UA38 5C073 AA02 AA03 AB07 BB02 CE01 CE04 5C076 AA22 BA09 BB13 CB01

Claims (10)

[Claims] 1. An image processing apparatus for reproducing JPEG-compressed image data, which comprises a reducing means for reducing the given JPEG-compressed data in MCU units, and invalidation when performing the reducing in MCU units by the reducing means. Reducing means for reducing the lost data, storage means for packing and storing each image block generated based on the result reduced by the reducing means, and output means for outputting the image stored by the storage means. An image processing apparatus comprising: 2. The image processing apparatus according to claim 1, wherein the reducing unit is positioned before the inverse DCT conversion process when decoding the JPEG compressed data. 3. The reduction means has a reduction magnification of S / 8 (S
= 1, 2, ... 8), M of the JPEG compressed data
S × with the DC component as the origin in the dequantized data of the CU
The image processing device according to claim 2, wherein the data of S is output as valid data and the other data is output as 0. 4. The reduction means has a reduction ratio of S / 8 (S
= 1, 2, ... 8), S × after the inverse DCT transform
4. The image processing apparatus according to claim 2, wherein the data of S is used as effective data and the other data is reduced and output. 5. When the JPEG image data is given, the reduction means, the reduction means, and the storage means generate a 1/8 reduced image, and the compression means performs JPEG compression on the 1/8 reduced image. Selecting means for selecting one of the JPEG compressed image data and the ⅛ JPEG compressed image compressed by the compressing means according to a designated magnification, and reducing the selected JPEG compressed image data by the reduction. The image processing apparatus according to claim 4, wherein the image processing apparatus outputs the image data via a means, a reduction unit, and the storage unit. 6. A method of controlling an image processing apparatus for reproducing JPEG compressed image data, comprising: a reducing step of reducing given JPEG compressed data in MCU units; and a reducing step in MCU units in the reducing step. A reduction step of reducing invalid data, a storage step of packing and storing each image block generated based on the result reduced by the reduction step, and an output of outputting the image stored in the storage step And a step of controlling the image processing apparatus. 7. A computer program which, when read and executed by a computer, functions as an image processing device for reproducing JPEG-compressed image data, comprising a program code of a reducing step of reducing the supplied JPEG-compressed data in MCU units. The program code of a reduction process for reducing invalid data when performing reduction in units of MCU in the reduction process and each image block generated based on the result reduced by the reduction process are stored together. A computer program, comprising: a program code of a storage process; and a program code of an output process for outputting an image stored in the storage process. 8. A storage medium storing the computer program according to claim 7. 9. An image processing apparatus for reading an original with a reading unit and printing it out, wherein image data obtained by reading with the reading unit is a JPE.
First storage means for compressing using the G compression means and storing in a predetermined storage means, reduction means for reducing the JPEG compressed image data stored by the first storage means in MCU units, and the reduction means. At the time of performing the reduction in the unit of MCU, the reduction means for reducing the invalid data and the image blocks generated based on the result reduced by the reduction means are packed to generate the reduced image, and the JPEG compression is performed. Second saving means for saving the reduced JPEG compressed image data in the storage means by means of the means, and JPEG compressed image data saved in the first saving means based on the reduction ratio designated at the time of preview display Alternatively, one of the reduced JPEG compressed image data saved by the second saving means is selected, and a preview table of the image data obtained through the reducing means and the reducing means is displayed. An image processing apparatus comprising: a display unit shown. 10. A method of controlling an image processing apparatus for reading an original by a reading means and printing it out, wherein image data obtained by the reading means is read by a JPE.
A first saving step of compressing using a G compressing means and saving it in a predetermined storage means; a reducing step of reducing the JPEG compressed image data saved in the first saving step in units of MCU; At the time of performing the reduction in units of MCU, the reduction process for reducing the invalid data, and the reduced image is generated by packing each image block generated based on the result reduced by the reduction process, and the JPEG compression is performed. A second saving step of saving the reduced JPEG compressed image data in the storage means using a means, and the JPEG compressed image data saved in the first saving step based on the reduction ratio designated at the time of preview display. Alternatively, one of the reduced version JPEG compressed image data saved in the second saving step is selected, and a preview table of the image data obtained through the reducing step and the reducing step is displayed. And a display step shown in the figure.